Auto-strip Nevo preambles and separate style analysis per appeal subtype

- Add strip_nevo_preamble() to extractor.py — auto-removes Nevo database
  headers (bibliography, legislation, mini-ratio) during training upload
- Add appeal_subtype column to style_patterns table — patterns are now
  stored per subtype instead of globally mixed
- Update clear_style_patterns() to support subtype-scoped deletion
- Pass appeal_subtype through analyze_corpus → store → upsert pipeline

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/tools/documents.py

@@ -152,8 +152,9 @@ async def document_upload_training(
     if source.resolve() != dest.resolve():
         shutil.copy2(str(source), str(dest))
 
-    # Extract text
+    # Extract text and strip Nevo preamble
     text, page_count = await extractor.extract_text(str(dest))
+    text = extractor.strip_nevo_preamble(text)
 
     # Parse date
     d_date = None